Control of carbon dioxide (CO.sub.2) and oxygen (O.sub.2) concentration around produce has been shown in the prior art to increase the storage life thereof. Control of water vapor concentration is also important. Conditions for the optimal storage of horticultural commodities are influenced by factors which include crop species, cultivar, growing conditions, maturity, quality, temperature, relative humidity, packaging, and storage duration. Storage under controlled and modified atmosphere is influenced by the concentration of oxygen, carbon dioxide, ethylene, water vapour and other gases. Controlled atmosphere (CA) storage is achieved by externally supplying a gas stream of the required O.sub.2 and CO.sub.2 concentration into the storage cold room. Controlled atmosphere packaging achieves extended produce life because of effects such as slowing respiration and inhibiting pathogen growth.
It is also known in the prior art that CO.sub.2 and O.sub.2 atmospheres surrounding produce can be modified by utilising the respiration behaviour of the produce where O.sub.2 is converted to CO.sub.2. With modified atmosphere (MA) packaging, produce is stored in polymeric film where the film permeability is exactly matched to the expected respiration behaviour as influenced by temperature and atmosphere changes to provide the optimum CO.sub.2 and O.sub.2 atmosphere.
A controlled permeability film, disclosed in International Patent Application PCT/AU91/00346, to applicants, the entire disclosure of which is incorporated herein by reference, has proved partially successful in alleviating some of the difficulties related to the prior art. However, the CO.sub.2 -O.sub.2 balance is significantly influenced by changes in ambient temperature. For example such a film may be designated to operate over a certain temperature range (e.g. 0.degree.-5.degree. C.) in cool stores. If the temperature of the package exceeds an upper limit (e.g. 10.degree.-15.degree. C.) for an extended period of time, the respiration rate of the produce becomes too high for external O.sub.2 to permeate through the film at a sufficient rate. The produce then respires anaerobically and soon dies.
It is also known in the prior art to rupture packaging in order to permit fumigation thereof as part of disease control and in order to satisfy import requirements in certain countries. However, the packaging rupture must be handled manually and is a time-consuming and thus expensive exercise.
Accordingly it is an object of the present invention to overcome, or at least alleviate, one or more of the difficulties related to the prior art.